min-nis



(No Model.) 5- Sheets-Sheet 11.

P. MINNIS. SWITGHBOARD FOR TELEPHONE SYSTEMS. No. 561,419. I PatentedJune 2, 1896.

v liar/anion Paal ANDREW B GFHNANLPHOYOUTHQWASHINGTUN 0C '(No Model.) 5Sheets-Sheet 2.

' P. MINNIS. SWITGHBOAR'D FOR TELEPHONE SYSTEMS.

N0. 561,419. Patented June 2, 1896,

ANDREW BERAHAM. PflDTp-UINQWRSHIN GTDNJAC 5 Sheets-Sheet 3.

{No Model.)

P; MINNIS, SWITGHBOARD FOR TELEPHONE SYSTEMS. No. 561,419.

jizuw/ioir AN DRE 'EGRIKAM. FNOYO'UTHO. WASIH N STONE D C.

-(No Model.) 5-ShEets-She6t 4.

P. MINNIS. V

SWITGHBOARD FOR TELEPHONE SYSTEMS. No. 561,419. Patented June-2, 1896.

71Z Z5Z6 ip'em Inventor M M 1 ml Jizbuea,

AN DREW B GRAHAM, moroumawAsnms'rou. D C

' 1 r 5 Sheets-Sheet 5.

. P. MINNIS. SWITOHBOARD FOR TELEPHONE sYsTEMs.

Patented June 2, 1896.

jizwenjar fazal flak llmrnn STATES PATENT QFFICE.

PAUL MINNIS, OF MOBILE, ALABAMA, ASSIGNOR OF ONE-HALF TO THE HOMETELEPHONE COMPANY, OF SAME PLACE.

SWITCHBOARD FOR TELEPHONE SYSTEMS.

SPECIFICATION forming part of Letters Patent No. 561,419, dated June 2,1896.

' Application filed February 17, 1896. Serial No. 579,647. (No model.)

A To (ti/Z whmn it may concern.-

' abridged, more rapidly and easily performed,

greater accuracy secured, and confusion and uncertainty removed in amarked degree; second, to provide a system of call-circuits,electric-lamp circuits, and switch-operating devices to cut thelamp-circuits in and out,

each lamp being placed in a call-box having a numeral or other characterdenoting one of the line-stations, the station thus indicated beingcomprised in a call-circuit which is completed through theswitch-operating device which cuts the lamp in the call-box into circuitand through a switch at the line-station which is normally open, wherebya subscriber can call the central station by merely closing the openswitch, without resorting to a magneto call-generator, the ignition ofthe lamp giving notice to the central station by illuminating a numeralor character on a transparent wall of the call-box; third, it is onepurpose of my said invention to provide automatic means for givingnotice to the central station of the cessation of communication betweenany two line-stations, such notice being the equivalent of the ringoffnow practiced in other systems, but differing therefrom in beingautomatically accomplished by merely releasing the hand-te1ephone,whichpermits the switch to open the lam p-circuit and extinguish the lamp inthe call-box, thus rendering it unnecessary for the person using thetelephone to ring-off or perform any other act except to remove the handfrom the instrument; fourth, it is my object to provide means wherebyany operator at a central station can ascertain in an instant whether awire over which communication is desired is in use.

My invention also comprises other novel features, all of which will befully explained hereinafter, and then particularly pointed out anddefined in the claims which terminate this specification.

To enable those skilled in the art to which my said invention relates toclearly understand and to practice the same, I Willproceed to describesaid invention in detail, reference being had for this purpose to theaccompanying drawings, in which Figures 1 and 1? constitute a diagramshowing the arrangement of circuits ata central station and between thelatter and two linestations. Fig. 2 is a central longitudinal section ofone of the plugs used in connecting the service-wires of twoline-stations through the line-jacks of the switchboard. Fig. 3 is aview in longitudinal section of one of the linejacks of the switchboard.Fig. 4 is a sectional View of the same, the section plane beingindicated by the dotted line at 4 in Fig. 7. Fig. 5 is afurthersectional view of the same, the section plane being denoted by the line5 5, Fig. 7. Fig. 6 is a transverse section upon the line 6 6 in Fig. 3.Fig. 7 is a cross-section upon the line 7 7 in Fig. 5. Fig. 8 is asectional view showing the electrically-operated switch for closing andopening one of the lamp-circuits, this view also including a diagram ofthe two circuits for lighting and extinguishing the lamp and a circuitfor the latter. Fig. 9 is a sectional view of the telephone used at theline-stations, showing the switch which completes the call-circuit, the

figure being in two parts.

The reference-numeral 1 in said drawings indicates generally the centralstation of a telephone system, and the numerals 2 and 3 denote two ofthe line-stations, the station apparatus, comprising the station-calland the parts of the telephone, being shown conventionally in Fig. 1. Itshould be stated that the system of circuits in which each linestationis connected by an independent service-wire to the central station andto a return-wire common to all the stations and to a single main batteryor source of electric generation is the same, substantially, as that setforth in an application filed by me of even date for a system oftelephonic communication, said case bearing Serial No. 579,647. Theline-station apparatus also, as

well as the switch-operating device, the plug,

- and the line-jack and plug combined, are

all subjects of separate applications of even date, and I make no claimin this case to any .of these parts separately. Being essential to mypresent invention, they are described in connection with it, but areclaimed only in those combinations in which the present invention isincluded.

Each line-station is conn eeted by a servicewire 4 to thecentral-station switchboard in the manner described hereinafter. Thesame wire also makes connection with a single return-wire 5 of suchdiameter as to equalize the aggregate resistance of the service-wires.This return-wire forms part of the path traversed by the currents fromall the servicewires. It is not connected to earth at any point, andthere is no ground upon any service-wire, so that I provide a completemetallic circuit for every line-station which is without earthconnection.

The return-wire 5 is connected by a tapwire 6 to one pole of a singlemain battery or source of electric energy B. This tap-wire also connectselectrically with a spread ter minal 7, which lies between thereturn-wire and the main battery. The other pole of said battery B isconnected by a wire 8 to a second spread terminal 9. From this spreadterminal a wire 1.0 is carried to the first terminal of the helices of apair of electromagnets 12, and from the second terminal awire 13 is ledto one of the line-jacks of the switchboard at the central station,which has two closed spring-contac ts latand 15, to the former of whichsaid wire 13 is connected. From the other spring-contact, 15, a wire 16goes to the multiples M of the switchboard, and from these multiples awire 18 is carried to a single spring-contact 19, which is in the sameline-jack with the closed contacts 14: and 15. From the single contact19 the service-wire 4 is led to line-station 2, where it forms a loophaving two branches between which the bell-coils 20 are placed inbridging connection. Beyond these coils the transmitter T and receiver Rare connected in series, and from these parts of the telephone onebranch of the loop is led to the return-Wire 5. The circuit, whichincludes the service-wire 4, single contact 19, wire 18, multiples M,wire 16, closed contacts 14. and 15', wire 13, electromagnets 12, wire10, spread terminal 9, wire 8, battery 13, tap-wire 6, and commonreturn-wire 5, is normally complete at every point except at theline-station, where a switch (shown conventionally in Fig. 1) is placedin the handle supporting the receiver and transmitter, as shown in Figs.9 and 10 and explained in detail hereinafter. This switch is normallyopen, and by closing it the person using the telephone is able to send acurrent from the battery B over the circuit last described. The actionof this current is as follows:

.The eleetromagnets 12 are arranged at the central station in convenientproximity to the switchboard and in full sight of the operators. Thereare a pair of these magnets for each line-station, the circuit in eachbeing similar to that already described. By reference to Fig. 8 it willbe seen that the pair of electromagnets 12 are mounted upon a base 21,from which they are insulated. Rising from this base is a post 22 ofconducting material, on which is accurately balanced an armature 23.Upon this armature is mounted a small glass tube 24, which is also inequilibrium so far as regards an equal apportionment of its weight uponboth sides of the fulcrum 25, on which the armature is balanced. lVithinthe tube, which is closed at both ends,is placed a globule of mercury26, which is free to run from end to end of the tube when the latter isinclined even slightly. Mercury is the only substance suitable for thispurpose, as it will move on a very slight inclination and with greatswiftness, so that an instantaneous tip of the armature will besufiicient to enable the mercury to travel past the center and depressthe end toward which it moves. The armature 23 forms part of the derivedcircuit, the extremity which is adjacent to the magnets 1.2 beingprolonged to form a contact 2", which rests upon the end of a secondpost 27. The wires 10 and 13 go, as already stated, to the terminals ofthe magnets 12. From the post 22 a wire 28 is led to a feeder 29 andfrom the post 27 a wire 30 is led to one terminal of a smallincandescent lamp 31. From the second terminal of the lamp a wire 32goes to a second feeder 33. These feeders are connected, respectively,to the opposite poles of the main battery B and are open or withoutcircuit, except through the multiple-arc connections to the lamp 31 andthrough similar connections to a lamp 31, identified with line-station3. Each of these lamps is inclosed in a small box or housing 34, havinga transparent wall 35, on which is displayed a number or characterdenot-in the line-station identified with that lamp. Thus by merelyclosing the switch at the line-station the lamp-circuit is establishedand maintained after the switch is released by the armature 23,overbalanced on one side by the mercury globule 2G. The means forcutting out the lamp-circuit will be explained in due course.

The end of the armature opposite that forming the contact 23 has aprolongation 36, which lies between two steps 37, both of which areadjustable in a post 38 upon the base 21. This post is insulated andforms no part of any electrical circuit. 'Zeneath the adjacent end ofthe armature 23 is a pair of electromagnets 39, insulated on the baseand similar in all respects to the magnets 12. The first terminal of themagnets 39 is connected by a wire +10 to a wire 41, which is led to onepole of the main battery B. From the other pole of said battery thecircuit of the magnets 39 is byway of a wire 42 to a wire 4:3, and bythe latter to a spring-contact 44, one

of a pair arranged in the same line-jack with the contacts 14: and 15.The second contact of the pair, denoted by the numeral 45, is ar rangedover the contact 44, but not in touch with it. From this secondspring-contact a wire 4:6 goes to the second terminal of the magnets 39.lVhen the operator at the central station answers a call and inserts theplug on one end of the flexible cord in the line-jack in the mannershown in Figs. 3, at, and 5, the conducting-cap upon the end of the plugengages the two contacts 4A and and closes the circuit, which includesthe helices of the electromagnets 39. This attracts thecorresponding'end of the armature 23, drawingit down and causing themercury globule to run to that end of the glass tube 24:, thusmaintaining the armature in the position it is caused to assume by theattraction of the magnets 39. The rise of the terminal-contact 23 breaksthe circuit of the lamp 31 and extinguishes it, its ignition being thecallsignal by which the central station was notified that line-stationNo. 2 desired to communicate with another station. Wires 47 go from thecontact M to the multiples of the switchboard, as shown convention allyin Fig. 1, these connections being so familiar as to require nodescription.

It is well known that in every central station of a telephone systemcomprising an average number of subscribers or line stations, or insystems serving even less than an average number, the switchboard isdivided into parts, each containing as many separate connections as canbe served by a single attendant, and containing, moreover, multiples orduplicates of all the remaining connections. I may mention, though itmay be unnecessary, that one purpose of these duplicate connec tions ineach of the divisions or panels of the switchboard is to enable any oneof the operators to connect a linestation served by that operator withany one of the line-stations served by an operator having charge ofanother division or panel, and to be able, moreover, to ascertaineasily, accurately, and instantaneously whether the line-station withwhich communication is desired is already using the service-wire whichconnects that station. to the switchboard.- It is one of the specialpurposes of my present invention to provide means for accomplishing thiswith absolute certainty with the minimum expenditure of time, care, andeffort or manual action on the part of the operators at the switchboard,

'and without the necessity of addressing a question to eitherline-station and awaiting a reply. The means I provide for this purposeare as follows: At the central station, in convenient proximity to theswitchboard, so that the attendants can readily see the same withoutchanging their position, I arrange a series of small lamps 4-9, eachidentified with one of the panels of the switchboard. Each lamp has itsown independent circuit, which is closed and opened in the manner I amabout to describe. One lamp-terminal is connected by a wire 49 to a post52, which forms a support for the armature 53 of a pair ofelectromagnets,which are arranged,when energized, to attract thearmature, which is normally raised by a spring or any other meanssuitable for the purpose. IVhen attracted, the prolonged end of thearmature is brought into contact with the post 54, and from said post 54a wire 55 is led to a feeder 56. This feeder goes to one pole of themain battery B and the other pole of said batteryis connected to asecond feeder 57. From the latter a wire 59 is led to the secondterminal of the lamp.

The magnets acting upon the armature 53 are denoted in Fig. 1 by thenumeral 60. The circuitby means of which they are energized is asfollows: From one terminal of the helices of said magnets 60 a wire 61goes directly to one pole of a battery 62. From the other pole awire 63goes to the spread terminal 7, from which point the circuit is by thetap-wire 6, return-wire 5, to the line'station. Here if the line isclosed the current passes through the telephone and over the servicewire4 to the single contact 19 in the linejack. Thence, a plug beinginserted in the jack, the path of the current is through contact-piece72, bushing 67, face-plate 68, conducting-strip 69 of the jack, andthence on by a wire 18 to the corresponding multiples M and to theirrespective face plates 68 through their respective contact strips 69.The circuit is completed bya wire 64: from the second terminal of theelectromagnets 60 to a test-thimble 65. This thimble is in form a devicecorresponding with its name, being worn by the operator upon one finger.It is made of some insulating material and has a metal tip 65, to whichwire 64 is attached. The pressure of this metal tip (55 against thefaceplate 68 of any line or multiple jack that is in use closes thetest-circuit, energizes the electromagnet 60, attracting the armature53, and drawing it into contact with the post '54., thus closing thecircuit of the lamp 49, by the ignition of which the operator isnotified that the service-wire thus tested is in use. Should the line beidle, the test-circuit Will be open between single cont-act l9 andcontact-piece 72 in the line-jack and all of its multiples, and it beingtherefore impossibe for the operator to close the test-circuit byestablishing the contact between the metal tip 65 of the test-thimble 65and the faceplate 68 of the corresponding jack in front of the operatorthe failure of the lamp 49 to burn indicates that the line tested isfree for use. To make the use of this testing device clear, I will nowrefer to the construction of the line-jacks and the plugs used therein.

Figs. 3 to 7 show one of the line-jacks, and Fig. Zone of the plugs.Each of the 1ine-jacks has a non-conducting body 66, containing theopening for the insertion of the plug. At its month this opening has abushing 67 and faceplate 68 of conducting metal. A conductingstrip 69connects at one end with the faceplate and extends to or a little beyondthe rearward end of the non-conducting body (36, lying for the greaterportion of its length in a channel 70, formed in the non-conductingmaterial. Diametrically opposite this strip 66 the single spring-contact19 is arranged, secured near one end to the outside rearward part of thejack, its forwardly-projecting portion lying in a longitudinally-formedslot 71, its free extremity extending beyond the slot and lying insidethe end of the bushing (37, and norm ally separated from a contact-piece7 2,which connects electrically with the bushing 67 and face-plate 68.

Upon the rearward end of the line-jack are mounted the twospring-contacts 44 and 45, diametrically opposite each other. Their freeends approach each other, but do not meet, their points projectingforward or toward the mouth of the jack and being curved to diverge, asshown in Fig. 3. These contacts are attached to the exterior faces ofthe non-conducting body 66, and their forwardly-projecting portions passinto slots 73, in order to enter the opening for the plug. Upon the samepart of the non-conducting body are mounted in a similar manner thecontacts 1st and 15, which pass into and through slots 74, theirforwardly-projecting ends meeting in the center of the opening. Thepoints of the contacts are bent away from each other or diverged toenable the end or the plug to enter between and separate them. Forconvenience in mounting these contacts the rear end of the jack may behexagonal, as shown in Fig. 6, and the opposite contacts are separatedfrom adjacent contacts by arcs measuring about sixty degrees upon thecylindrical surface of the jack.

The wires 43 and 46 are connected to the contacts ll: and 45,respectively. From contacts 41-1 and are carried wires -17 and 47,respectively, to the corresponding contacts of the correspondingmultiple jacks of the switchboard. \V ire 13 is connected to contact 14,and from opposing contact 15 is carried wire 16 through the contacts ofthe corresponding multiple j acks of the switchboard correspond in g tothe contacts 14: and 15 of the corresponding line-jacks. Wire 4 isconnected to contact 19, from which is carried wire 18 to thecorresponding contacts of the coresponding multiple jacks of theswitchboard. From contact-strip 69 is carried wire 18 to the corresponding contact-strips of the corresponding multiple jacks of theswitchboard. Beyond the last corresponding multiple jack of theswitchboard wires 10 and 18 are connected to gether, whilethe ends ofwires 47, 1-7, and 18 are left free and are tapped or otherwiseinsulated to prevent any short circuit with other wires or parts of theswitchboard. Tires 16, 18, 18, 4:7, and 4:7 are designated and known asthe multiple wires of the switchboard, wire 16 being the annunciator-muttiple, wire 18 the line-multiple, wire 18 the test-multiple, and wires47 and t7 the first and second restoring-multiples.

The plug shown in Fig. 2 has a point of non-conducting material, its tipbeing covered by a cap 7 (J of conducting material. The reduced portionof the point enters a tubular body 77 between the end of which and thethimble 7 6 the enlarged non-conducting portion of the point is exposed.A non-conducting sleeve 78 incloses most of the tubular body, andbetween the end of said sleeve and the exposed part of thenon-conducting point a portion of the conducting body 77 is exposed. Acollar 7 9 is formed on the exterior of the sleeve 7 S to limit theinsertion in the line-jack, this collar being placed at such a pointthat when it abuts on the face-plate G8 the conducting-cap 70 willengage the ends of contacts ii and 45, while the contacts 14 and 15 willbe separated and will rest upon the exposed non-conducting portion ofthe point 75, as seen in Figs. 3 and 4. The single contact 10 will atthe same time rest against the exposed portion of the conducting tubularbody 77, the point of said cont-act being forced against thecontact-strip 7 2, as shown in Fig. 5 in dotted lines.

Upon the open end of the sleeve is placed a cap 80, formed ofinsulatingmaterial and connected by screws 81, which pass through slots82 in the cap and are tapped into the sleeve 78 and tubular body 77. Aspring 83, coiled between the end of the sleeve and the closed end ofthe cap, holds the latter normally in the position shown in Fig. 2,permitting the cap, however, to be moved toward the open end of thesleeve by pressure.

In the tubular conducting-body 77 is a core 84: of conducting material,which is connected to a wire 90. In the center of the cap is inserted aring 86 of conducting metal, having a diameter equal to that of thetubular body, with which it is substantially concentric. \Vithin thisring lies a cylindrical bushing 87, which projects a little inside thecap and enters the tubular body 77 when the cap 80 is pushed up. Thewire enters through thisbushing, and a second wire 88 is connected tothe ring 86. These two wires are contained in one part of the dividedflexible cord shown in Fig. 1. From binding-post Sf) wire 96" goes toone pole of battery 96 and from the other pole of this battery ontobinding-post 89, and thence on through the other part of the dividedcord to core 8% of the other plug of the pair. In said figure the wire85 goes to a binding-post 89 on the apron 90. In the first plug of thepair wire 88 goes to a binding-post 91, and thence to the head-phone 92of the operator at the central station. From the headphone a wire 93returns and goes to the spread terminal 7. In the other plug of the pairthe wire 88 goes to binding-post 91, and thence to one pole of amagneto-generator 92*, from the other pole of which wire 93 goes to thespread terminal 7.

If station 2 is talking, and if a call comes to another panel of theswitchboard to con nect said station 2 with the person calling, theoperator, who knows nothing about station 2 except through the multiplesof the board, must first ascertain if the service-wire from station 2 isin use. To do this, the metal tip of thimble 65 is pressed against thefaceplate 08 of the jack corresponding to line station 2. A circuit isthus completed over the following path: beginning at faceplate 08,through contact-strip 69,test-1nultiple 18, to the contact-strip 69 ofthe corresponding jack in use at the time by line-station 2, through thefaceplate 68, bushing 67,0011 tactpiece 72, and line-contact 19 of thatjack, and thence on over service-wire 4 to line-station 2, through thetwo branches of the loop in service-wire l at that station, overreturnwire 5, tap-wire 6, to spread terminal 7, thence on by wire 63 toone pole of battery 62, from the other pole of battery 62 to oneterminal of electromagnet 60, and from the other terminal ofelectromagnet 60, overwire 64:, back to metal tip 65 of thimble 65. Thecircuit of the electromagnet 60 being thus completed, armature 53 isdrawn by it into contact with post 54, thus closing the circuit of lamp4.9, the ignition of this lamp notifying the testing operator that thewire is in use at the line-station 2.

The two parts of each flexible cord at the central station areconnected, respectively, to the opposite poles of a battery 96, which Iterm a talking-battery. The poles of this battery are connected to thewires 85 and 85, respectively, in the two parts of the cord, so thatwhen the plugs are inserted to put the line-stations in communicationthe circuit beginning at one pole of battery 96 will be by way of a wire96" to binding-post 89, wire 85 to binding-post 89, thence on to thefirst plug of the pair, thence through its conductingbody '7 7,line-contact 19 of the jacks, servicewire 4, to the line-stationcorresponding to that service-wire and through the two portions of theloop of the service-wire at and the telephone therein to the return-wire5, thence along return-wire 5 to the line-station of the service-wirecorresponding to the jack into which the plug of the other part of theflexiblc cord is inserted, over the two portions of the loop of thissecond service-wire and the telephone therein, and on over this secondservice-wire to its corresponding jack in the switchboard at the centralstation, over contact 19 of said jack to conducting-body 77 of theinserted plug, and thence by wire 85 to binding-post 89*, and on to theother pole of battery 96.

The operators head-phone 92 is connected by wire 88 in one part of theflexible cord and wire 93 between the cylindrical bushing 87 of the cap80 of one of the plugs and spread terminal 7. The magneto-generator 92is similarly connected between cylindrical bushing 87 of the cap 80 ofthe other of the plugs and spread terminal 7 by wires 88 and 93,respectively.

I have the two plugs made in two colors, all those to which thehead-phone circuit is connected being of one color and commonlydesignated as the first plug of the pair, and all the plugs to which themagneto-generator circuit is connected being of another color andcommonly designated as the second plug of the pair. The circuits for thehead-phone and the magneto-generator, respectively, are normally open inthe caps of their respective plugs between the cylindrical bushing 87 inthe cap 80 and the conducting-body 77 of the plug. When a subscribercalls the central office, the force necessary to insert the plug in thatsubscribers jack telescopes the cap 80 on the body 78 of the plug,closing the contact between the cylindrical bushing 87 of the cap andthe conducting-bod y 77 of the plug, thus completing the circuit of theoperators head-phone 92 over the conducting-body 77 of the plug, contact19 of the jack, the service-wire to the line-station, over the twopertions of the loop in the service-wire at the line station, returnwire5, tap-wire 6, spread terminal '7, wire 93, to the head-phone, thence onby wire 88 to one pole of battery 90, and on from the other pole ofbattery 90 to bindingpost 91, and from binding-post 91 back tocylindrical bushing 87 of the cap 80. The talk ing-battery for theoperators head-phone (designated as 90) is placed in series with theWire 88 after it leaves the binding-post 91, all of the bindingposts 91on each panel of the switchboard being connected by a common strip forthat panel and being cond noted on from that strip by a single wire 88,the same being common to all the independent wires 88, one in each ofthe portions of the flexible cords connected to the first plugs of thatpanel or" the switchboard. By the term operators head-phone I mean both.the receiver and transmitter, as shown in Fig. 1.. The operatorshead-phone being brought into connection with the calling-subscribe1"sstation automatically, as just described, the operator can promptlyascertain the wants of that subscriber. Should the calling subscriberrequest connection with some other line-station, the operator insertsinto the jack of the called-subscribefs line the second plug of thepair, the force required to insert the plug automatically telescopingthe cap on the body of the plug, setting up a contact between thecylindrical bushing 87 of the cap and the conducting-body 7 7 of theplug, thus completing and establishing a circuit carrying in seriestherewith magneto-generator 92, by which the electromagnet of the bridgin g-bclls at the called-subscribers station are energized and thebells rung, notifying that subsubscriber that he is wanted at histelephone. The path of this ringingeircuit is substantially similar tothat of the head-phone circuit already described, with the substitutionof wires 88 and 93 for wires 88 and 93, respectively.

In the ringing-circuit wire 88 corresponds to wire 88 in the head-phonecircuit, there being an independent wire 88 from the second plug of eachpair to each of the bindingposts 89, all of these binding-posts on eachpanel of the switchboard being connected together by a common strip forthat panel and being conducted on from that strip by a single wire 88 tothe magneto-generator 92. The release of the plug by the operator cutsout the head-phone circuit of the ringing-circuit, as the case maybe, bymeans of the spring 83, which forces the cap back to its normalposition, thus breaking the contact between cylindrical bushing 87 ofthe cap 80 and conducting-body 77 of the plug. Either of these circuitscan, however, be instantly reestablished by a pressure of the operatorsfinger upon the cap of either plug; but should it become necessary toring the calling subscriber or speak to the called subscriber the plugsmust be reversed. In other words, all talking or listening must be doneby the operator by means of the first plug of the pair and all ringingby means of the second plug of the pair. The simplicity, speed, andcertainty secured by this arrangement will be readily appreciated.

From each of the binding-posts 80 on apron is led a wire 07 to oneterminal of the electromagnets 08, and from. the other terminal ofelectromagnets 98 a wire 90 goes to one pole of an independent battery100, from. the other pole of which wire 101 is led to the spreadterminal 7. Electromagnet 08 is provided with a post 102, which carriesan armature 103, normally held out of contact with a second post 104 bya spring or other contrivance. From post 102 a Wire is led to oneterminal of lamp 105, from the other terminal of which wire 110 goes towire 10!), wire 109 going to one pole of main battery B, and being oneof a pair of common open-circuit feedwires with which all thelamp-circuits of the switchboard corresponding to the circuit of lamp105, now being described, are in multiple arc. \Vire108 is the other ofthis pair of comm on feed-wires and goes to the other pole of mainbattery B. From wire 108 a wire 107 is led back to post 104.

The above-described circuit,with all its appurtenances, provides what Iterm an automatic ring-oft, as it accomplishes the work at present doneby the arrangements and appliances known as ring-oft devices. Theoperation of this ring-oil, briefly described, is as follows: Itscircuit is over the following path: from one terminal of electromagnet98 over Wire 97 to binding-post S9, thence by wire 85 to conducting-core8% of the plug, through conducting-body 77, containing core 84, tocontact 10 of the jack, from contact 19 over service-wire 4 to theline-station, over both portions of the loop of the service-wire, andthrough the telephone and its connections at the line-station toreturn-wire 5, thence on over tap-wire 0 to spread terminal 7, fromspread terminal 7 over wire 101 to one pole of battery 100, and from theother pole of battery 100 by wire 00 to the other terminal ofelectromagnets 08. This circuitis normally open in the switch in thehandle of the telephone at the line-station. \Vhen the subscriber closesthis switch, in order to cut his transmitter and receiver into circuit,the ringoff circuit is established, the electromagncts 08energize,'armature 103, attracted into contact with post 104, closingthe lampcircuit and igniting lamp 105.

It is obvious that as long as the subscriber has his telephone in usethe ring-off circuit will remain intact and the lamp will continue toburn and that as soon as he releases the handle of his telephone thespring-switch in the handle will open, disestablish the ringoff circuit,and by the consequent release of armature 103 open the lamp-circuit andextinguish the lamp 105, thus notifying the operator that the twoline-stations connected together by the corresponding pair of cords andplugs have completed their conversation and that these two service-wiresare ready to be disconnected. It will be observed that I run thering-off circuit through binding-post 80 and to the first plug of thepair, so that the calling subscriber always controls the circuit. Thisarrangement also enables the calling subscriber to recall the operatorat any time by manipulating the switch in the handle of his telephone,which manipulation will result in the flashing or intermittent ignitionand extinguishment of lamp 105. Each first plug of the switchboard isprovided with one of these automatic ring-off circuits.

In order to prevent the batteries 00, 90, and 100 or any two thereoffrom short-circuiting through each other when brought in contact, bymeans of a plug and jack, with any service-wire, they are placed withtheir similar poles toward the plug connection. Thus, although all threeor any two of these batteries may be connected to one service-wire atthe same time, establishing two or three similar circuits whose currentsall travel over a partially common path, there can be no commingling, asthey will be either all negative or all positive at the point where theyenter upon the common path.

Although the connections of the telephone at the line-station are onlyconventionally related to the subject-matter of this case, and as theyare covered with separate applications of even date herewith in orderthat the manner in and the means by which the subscriber controls thatportion of the appliances of the switchboard representing hisline-station. may be fully understood, I have shown in Figs. 0 and 10the detail arrangements of the telephone and its connections,particularly the switches in the handle of the telephone. Theseappliances may be described, briefly, as follows: In Fig. 9 the numeral111 denotes IIO one half of the handle of the telephone, and in thefigure the numeral 111 denotes the other half of the handle. In the twofigures the numerals 112 and 112 denote a chamber formed by the junctureof 111 and 111, in which chamber plate 113 is partially buried. Plate113 is pivotally mounted at one end and projected at the other end alittle'distance outside the handle, the degree of pro jection beingcontrolled by screw 114C, lying in notch 115 in the end of the plate. Anelastic conducting-strip 116 bears against the interior edge of plate113, normally pushing it out as far as permitted by screw 114. \Vhen thehandle is grasped, the pressure upon the projected edge of plate 113forces it inward and presses the end of elastic strip 116 into contactwith strip 117, which is secured by a screw to the bottom of thechamber. This contact closes the circuit of the line-station over thefollowing path: over strip 117, by wire 118, to one terminal oftransmitter T, from the other terminal of the transmitter, over wire122, strip 121, and terminal wire 123, to one branch of the loop in theservicewire, over the service-wire to the central station, by the pathin the switchboard and central-office connections, previously described,to return-wire 5, and back to the other branch of the loop in theservicewire, thence on over that loop, terminal wire 127 to elasticcontactstrip 124, thence over wire 128 to one terminal of the receiverR, and from the other terminal. of the receiver over wire 120 back toelastic contact 116. The path just described is the one taken by thecircuit set up by the contact between elastic strip 116 and strip 117when the subscriber is not connected with any other line-station at theswitchboard. \Vhen such a connection has been established, the path isthrough the spring-jacks, plugs, cord, and talkingbattery at the centralstation, thence on over the service-wire to the line-station with whichthe subscriber is connect-ed, through the loops in the service-wire andthe telephone and its connections therein at that line-station to return-wire 5, and thence back to the original line-station and over the pathalready described, the paths through the telephone and its connectionsat both line-stations thus connected being similar. Elasticcontact-strip 124 is secured by screw 125 at one end, its other endbeing free. Numeral 126 denotes a pusher lying behind the free end ofstrip 124. The other end of this pusher protrudes above the surface ofthe handle, and by pressure upon it with the thumb or fingert-hc strip121 can be brought into contact with strip 121, thus completing a shortcircuit between terminal wires and 127 through strip 124: without incorporating the other contact strips and wires and the receiver andtransmitter in its path. This short circuit goes through thecorresponding annunciator at the switchboard over the path alreadydescribed and is used for controlling that annunciator, although thelonger circuit closed by pressure upon plate 113 will accomplish and canbe used for this purpose. The legitimate use of plate 113 is to completethe circuit through the transmitter and receiver for purposes ofconversation, and also for calling the operator after the operator hasonce answered the annunciator-call and out the annunciator-circuit outby the insertion of the first one of the pairs of plugs of theswitchboard, as already described. The two halves 111 and 111 of thehandle, plate 113, and pusher 126 are of non-conducting material, allthe contact-strips and connections being of conducting material.

It will be observed that the insertion of the plugs in the line-jacksnot only breaks the call-circuits, which include the contacts 14 and 15,but it also completes the circuit of the magnets 39, which restore thearmature 23 to its original position, thus cutting out the circuit ofthe lamp 31. The circuit of the magnets 39 is completed through thecontacts 44 and 45 and the metallic cap 76 on the tip of the plug.

The purpose of opening the call-circuit by the insertion of the plug inthe line-jack is not merely for the prevention of short circuiting orleakage of the talking-current, but is for the very essential purpose ofdisestablishing the connection between the line and the main battery B.The heavy current from this battery must be removed from thetalking-circuit, because if it be present conversation would bepractically impossible. In this connection I will remark that the substitution of lamps for bells as means for calling the central stationgives me a silent switchboard, the quiet of which is only interrupted bythe low tones of the operators in speaking to calling subscribers. Thesubstitution of this tranquility in place of the indescribable clamorand interminable clanging of a large central station using the bellcallsremoves one of the severest and most injurious strains upon the nervoussystem of women that modern civilization has developed. Such a board,moreover, secures not only silence but speed to a degree -far superiorto anything heretofore used, and adds greatly to the convenience of boththe snbscriber and operator. For example, if the former desires to speakto the operator, instead of hanging up his hand-telephone on agravity-switch or operating said switch with one hand and the magneto inhis boX with the other hand he simply presses the switch in histelephone-handle several times in quick succession, thereby producing aseries of flashes from the lamp which the operator instantly seesandanswers, and, in other respects as set forth in the specification atvarious points, the changes effected by my invention simplify and reducethe labor of the operator, enable the switchboard to be accurately,promptly, and rapidly served by a much smaller force than has beenrequired under other systems, and in all respects improve the service.

lVhat I claim is 1. In a telephone system, a switchboard having each ofits flexible cords divided in two parts, one wire in each part connectedto the poles of a talking-battery, and the other wires tothe headphoneand to one pole of a call-generator, respectively, the ends of saidcords having plugs in which one wire is connected toa conducting-bodyand the other to a contact carried by a non-conducting spring-projectedcap movable on the end of the said plug to couple the wireselectrically, a visual call-signal corresponding to each line-station, acircuit for said signal comprising a balanced armature, and a contactfor one end of said armature, clectromagnets to attract each end of thearmature and independent circuits for said magnets, one circuitincluding a normally-open switch at a linestation, and the other circuitcomprising separated contacts in the line-jack of the switchboard, whichare coupled electrically by a conducting-cap on the tip of the plug,substantially as described.

2. In a telephone system a visual call-signal for each line-station,such as an electricallyilluminated call-box, a circuit for the samecomprising a balanced arm ature and a contact for one end of saidarmature, electromagnets to attract both ends of said armature,independent circuits forsaid magnets, one circuit including a normallyopen switch at a linestation and normally-closed elastic contacts in theline-jack which corresponds to said station, and the other circuitincluding rigid separated contacts in the line-jack, a plug having aconducting-cap on its tip to couple said contacts electrically when theplug is insorted and thereby complete the circuit of the elcctromagnetsby which the armature is attracted to break the sign al-circuit saidplug being also provided with a min-conducting point behind its tip toseparate the closed elastic contacts in the line jaclc P dividedflexible cord one part attached to each plug, one wire in each partbeing connected to ole pole of a talking-battery, the second wire in onepart to the head-phone and the second wire in the other part to one poleof a callgenerator, a non-conductin g sprin g-proj ected cap carrying acontact to which one wire in. each part is connected, a cond neting-body part of the plug to which the other wire in each part isconnected, and a spring-contact connected to a service-wire and arrangedin the line-jack to electrically engage the conducting-body of the plugwhen the latter is inserted, substantially as described.

3. In a telephone system, a switchboard having the two parts of eachdivided flexible cord connected to the opposite poles of a primarybattery, one wire in each part being connected from the battery to theconductingbody of the plug, and the other wire in one part to thehead-phone and in the other part to a call-generator, each of thelast-named wires being connected to a contact-ring in a movable cap 011the plug, and a line-jack for the plug having a single spring-contact tobear on the tubular conducting-body of the plug, a contact-piece,bushing, face-plate and contact-strip, into contact with which thesingle spring-contact is brought by the insertion of the plug, for theclosing and establishment of a test-circuit to the face-plates of thecorresponding multiple jacks of the switchboard two contacts normallyclosed to complete a call-circuit and separated by an insulating portionof the plug, and two normally-separated contacts to engage aconducting-tip on the plug and complete a circuit by which thecall-signal is restored to position, substantially as described.

4:. In a telephone-switchboard,the combination with the line-jacks andplugs of contacts which compete a circuit for communication between twoline-stations over service-wires and a common return-wire,spring-contacts arranged in the line-jack and normally closed to formpart of a call-circuit, and having their ends adapted to be separated bythe insertion of the plug, a visual call-signal operated by said circuitwhich includes a normally open switch at the line-station correspondingto said jack, and contacts normally separated but electrically connectedby the plug, to com plete a circuit by which the visual signal isrestored to its original condition, substantially as described.

5. In a telephone system, the OOlllldllZa'tlOll with a central stationand a series of line-stations of a s ngle w re common to all the linestations, a series of service-wires connecting the line-stations to theswitchboard at the central station and to said single wire, a testsignalconsisting of a lamp for each mu ltiple switchboard, a circuit for eachlamp i ncludin g a switch-armature and a suitable generator ofelectricity, and a testing-circuit comprising a separate test-batteryfor each multiple switchboard, electromagnets in the circuit of thetest-battery, to attract the switcharmature, a test-thimble, the mutiples of the switchboard, a conducting face plate and bushing in eachline-jack, and the service and return wires, over which communication isin progress, whereby the test may be made it lthout in terrupt-ing, orinterfering with the communication between connected line-stations,substantially as described.

6. The combination with a switchboard of a telephone system of acall-signal such as a lamp, a main battery, service-wires connecting theline-stations to the switchboard and to a common return-wire opencircuit-feeders connected to the poles of the main battery,lamp-circuits from said feeders, a balanced armature forming part ofeach lampcircuit, a glass tube mounted on each arLnature and containinga glob 1116 of mercury, a group of electromagne ts under one end of theIIO armature, a circuit for said magnets including the service-wires andreturn-wire and a normally open switch in each telephone, a group ofmagnets under the other end of said armature and a circuit for thelatter magnets including separated contacts in the line-jack and aconducting-tip on the plug, substantially as described.

7. The combinationwith a switchboard of a telephone system, of a seriesof automatic rin g-off circuits, each of such circuits operated by anindependent primary battery, one of such circuits connected to the firstof each pair of plugs of the switchboard through one of the conductorsof its portion of the flexible cord, each of said ringofE circuitscomprising a small independent battery, and an electroniagnetcontrolling an armatureswitch by which alocal circuit is opened andclosed, each of said local circuits being provided with an independentvisual signal such as a lamp and all of such local lamp-circuits beingsupplied with current from a common pair of feed-wires from the twopoles of the single main battery, each of said ring-off circuitsincluding, when in use, one of the ring-off batteries, one of theelectromagnets, the return-wire, one of the service-wires, one of theplugs and one of the conductors in its corresponding portion of theflexible cord of the switchboard by which connection is made with theservice-wire through the spring-jacks or their multiples, the linespring-contact of one of the spring-jacks of the switchboard, the loopand telephone at one of the line-stations and the switch in the handleof the telephone normally open when the telephone is not in use andclosed by the grasp 011 the handle of the telephone by the person usingit, substantially as described.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

PAUL MINNIS. lVitnesses:

CLAYTON B. CLARK, WILLIAM H. SULLIVAN.

